In-situ Detection Of Interfacial Photo-catalysis Induced Thermal Effect Using Optical Fiber Sensor

With the increasing demand of energy in the world,humankind have to face the serious problems that shortage of traditional fossil energy and the destruction of environment and climate such as greenhouse effect.Therefore,green environmental protection and sustainable energy development have gradually become the theme of human concern.Developing new energy is the only way to solve the present predicament.Thus,catalytic technology,as the key to improve the efficiency of new energy production capacity,has been taking central stage in development all over the world.Since sunlight is the main energy source of human beings,photocatalysis is the most concerned technology.In this study,researchers mainly focus on the process that photo generated carriers,but ignore the influence of photothermal effect.The reason is that current methods and techniques for accurate measurement of heat production in photocatalytic process are very limited,especially for the catalytic reaction in liquid environment where thermal measurement will be accompanied by large errors invitably.For example,the thermal imager can not precisely detect the photocatalytic heat on the “surface” of the catalyst.However,the photothermal effect plays an important role in the catalytic reaction,particularly for the photocatalysts with strong photothermal effect,which dominates the improvement of the overall catalytic efficiency.Therefore,accurate measurement of thermal effect in catalytic process is of great significance.In order to realize the real time,in situ and accurate measurement of the photothermal response of catalytic materials,an optical-fiber temperature sensor integrated with photothermal materials was proposed,by using a highly tilted fiber grating coated with carbon nanotubes and gold film.The details are as follows:(1)An integrated sensor for generating and measuring heat was designed and fabricated,where carbon nanotubes were coated to achieve heat generation during the photocatalysis in the infrared band,and the catalytic heat generation can be accurately measured in real time through the inclined grating inside the fiber.According to the wavelength shift of the resonance mode in the fiber,combined with the temperature sensitivity coefficient of100 ℃ / nm,the corresponding temperature change can be obtained.At the same time,in order to analyze the influence of heat on the electrochemical reaction,a gold film was coated on the surface of the optical fiber,which not only eliminates the sensitivity of the resonance modes to the environmental refractive index,but also endows the optical fiber sensor with the ability of conducting electricity,therefore can be used as the working electrode of electrochemistry to run the electrochemical reaction.(2)Two photocatalytic reaction models in two liquid media(paracetamol and ethanol)were set,to verify the dual-ability of conducting and detecting heat of the sensor.The experimental results showed excellent conductivity and catalytic performance of the sensor.Besides,it can be seen that the temperature change of catalyst can be detected as high as 14.0 ℃,and the real-time in-situ temperature detection with accuracy of 0.1 ℃ and response speed of 1.5 s is realized(3)Based on the data collected simultaneously by optics and electricity,the relationship between temperature and catalytic activity on the liquid-solid catalytic interface was successfully constructed.In conclusion,the optical-fiber photothermal sensor can be used as an excellent characterization tool to provide researchers with an effective method and tool for in-situ,real-time and accurate measurement of catalyst thermal effect and thermoelectric catalysis.